Well‐defined star‐shaped poly(p‐benzamide) via chain‐growth condensation polymerization: Use of tetra‐functional porphyrin initiator to optimize star polymer formation

Synthesis of a variety of star‐shaped polybenzamides via chain‐growth condensation polymerization with tetrafunctional porphyrin initiator

“…Recently, we have reported that the polymerization of the methyl ester of 4‐aminobenzoic acid 1b bearing N ‐TEG side chain was not controlled, whereas the phenyl ester counterpart 1b ′ underwent chain growth condensation polymerization at −20 °C to yield well‐defined poly( p ‐benzamide) bearing TEG side chain 6. In the synthesis of well‐defined star poly 1a , however, a higher polymerization temperature compared to the temperature for the synthesis of linear poly 1a was necessary to suppress concomitant formation of the linear polymer 2. Accordingly, the polymerization of 1b ′ with 2 ([ 1b ′] 0 /[ 2 ] 0 = 40 and 80) was examined at −10 °C and above (Table 1).…”

“…In chain‐growth condensation polymerization for linear poly( m ‐benzamide)s, the monomer is slowly added to a solution of initiator and LiHMDS,8, 9 so that the monomer concentration in the reaction mixture is lower than that in the chain‐growth condensation polymerization for poly( p ‐benzamide)s, in which the monomer was added at once into a solution of initiator and LiHMDS 2. Therefore, self‐condensation of the monomer in the synthesis of star‐shaped poly( m ‐benzamide)s from tetra‐functional initiator 2 would be suppressed under the same conditions that yield linear poly( m ‐benzamide)s. Thus, a variety of meta‐substituted monomers 3 were polymerized with 2 at 0 °C in the presence of LiCl13, 14 for N ‐alkyl and N ‐OOB monomers8 or N,N,N ′, N ′‐tetramethylethylenediamine (TMEDA)15–18 for N ‐TEG monomer10 according to the reported polymerization method for linear poly( m ‐benzamide)s (Scheme , Table 4).…”

“…Accordingly, UV–visible spectra of star poly 1b ′ in aqueous solution, in THF and as a thin film were measured. For comparison with these spectra, the spectra of star poly 1a with a hydrophobic N ‐octyl group, synthesized in our previous study,2 were also measured (Table 5). The UV–visible spectra of a solution of star poly 1a and star poly 1b ′ in THF showed the same Soret band and Q‐band, irrespective of the degree of polymerization (DP) of the arm of the star polymers (entries 1, 3, 5, and 8).…”

“…Most star polymers have flexible arms consisting of coil polymers, whereas we have synthesized star polymers having semi‐rigid aromatic polyamide arms, with the aim of obtaining star polymers with novel properties arising from the high intermolecular forces among the semi‐rigid arms. In a previous report,2 we described the synthesis of four‐arm star‐shaped poly( N ‐octyl‐ p ‐benzamide) by chain‐growth condensation polymerization of methyl 4‐(octylamino)benzoate ( 1a ) with porphyrin‐cored tetra‐functional initiator 2 . In this star polymer synthesis, self‐polycondensation of 1a occurred as a side reaction, leading to formation of linear poly 1a .…”

Synthesis of well‐defined aromatic polyamide‐graft‐poly(tetrahydrofuran) by chain‐growth condensation polymerization of macromonomer

“…As those reports, however, chain‐growth condensation polymerization has been used to control the degree of polymerization and the polymer end groups of condensation polymers, and polymers grafted with well‐defined polyphosphazene, poly(alkylthiophene), and aromatic polyamide were obtained. Conversely, graft copolymers with a condensation polymer backbone controlled by means of chain‐growth condensation polymerization of a macromonomer having a polymer side chain would be a challenge, because chain‐growth condensation polymerization is liable to be accompanied with self‐polycondensation when the monomer reacts with a sterically congested polymer end group . In this article, we describe the synthesis of well‐defined aromatic polyamide grafted with poly(tetrahydrofuran) [poly(THF)] by means of chain‐growth condensation polymerization of 4‐aminobenzoic acid ester macromonomers 1 having poly(THF) on the amino group.…”